1. Field of the Invention
The invention relates to load hauling machines and, more particularly, relates to a xe2x80x9cpower buggy,xe2x80x9d i.e., a relatively small, self-propelled load hauling vehicle having a storage bucket and operator""s controls. The invention additionally relates to a power buggy designed to maximize operator safety, stability, and comfort.
2. Discussion of the Related Art
Power buggies are well-known light industrial vehicles designed to haul loads of from a few hundred pounds to a few tons. The typical power buggy comprises 1) a chassis supported on the ground via a plurality of wheels, 2) a storage bucket or dumping platform supported on the front end of the chassis and liftable to dump loads, and 3) a power source for propelling the vehicle and for operating other powered equipment on the vehicle. The typical power buggy is controlled by an operator who is stationed behind the power buggy and who either walks behind the power buggy or stands on an operator""s platform mounted on the rear end of the chassis.
Controls for the typical power buggy include a steering control mechanism, a speed control mechanism, an engine kill switch or similar controller, and dump controls which raise and lower the bucket to dump hauled articles. The vehicle is steered by a generally Y-shaped handlebar having a pair of handgrips. Vehicle propulsion is controlled by a squeeze lever mounted adjacent one of the handgrips. Power buggies of this general type are available from Miller, the Morrison Division of Amida Industries, Inc., the Whiteman Division of Amida Industries, Inc., and Schroeder Industries.
The typical power buggy has several disadvantages impairing operator comfort and even risking operator injury.
For instance, the controls of the typical power buggy are inconveniently located and/or difficult to operate. As an example, the squeeze lever used for speed control operates on generally the same principle as a motorcycle hand brake to the extent that the operator must simultaneously grasp the handgrip and pull a spring-loaded lever towards the handgrip. The vehicle is propelled at a speed proportional to the amount of force applied to the squeeze lever. The squeezing action on conventional buggies is somewhat difficult for the operator, and prolonged operation of the squeeze lever can result in operator hand fatigue.
Additionally, conventional power buggies use a radial ball-type piston pump, such as the Eaton pump Model 1120 used in the Whiteman power buggy. The typical radial ball-type piston pump provides undesired feedback to the squeeze lever that increases with increased load. For example, as the pressure increases when, e.g., the power buggy climbs a hill, the internal pressure built in the pump rises and opposes the actuating force imposed on the pump""s swash plate, tending to re-center the swash plate. These conditions increase resistance to squeeze lever movement, hence raising the operating forces required for squeeze lever operation. This requirement for an increased amount of force accelerates operator fatigue. Furthermore, a radial ball-type piston pump can free wheel, leading a potential runaway condition when the buggy is traveling downhill.
In conventional power buggies, directional control, i.e., shifting between forward and reverse, is effected by way of a separate shift control lever located remote from the squeeze lever. The operator must release one of the handgrips to shift between forward and reverse with resultant risk of loss of vehicle control. This risk is heightened by the fact that speed control and directional control are independent. It is therefore possible for an operator to shift the vehicle while still actuating a squeeze lever, in which case the vehicle reverses its direction of travel abruptly, thereby potentially causing the operator to lose his/her balance.
Conventional directional control levers used in power buggies include three positions: forward, reverse, and neutral, with the neutral position being located between the forward and reverse. In switching from forward to reverse, the lever must travel through neutral. While the lever is in neutral, the power buggy can freely move. If the power buggy is on an incline while in neutral, the power buggy can uncontrollably roll, a problem that is further troublesome when the buggy is loaded.
In some power buggies, as the unit picks up speed when the vehicle is rolling down a hill under power, the hydraulic motors for the wheels are accelerated by the wheels. Above a certain speed, the motors, in effect, turn into pumps that can overpower the pump, leading to a runaway condition. If the operator tries to regain control by reversing the flow of hydraulic fluid to the wheel drive motors, the machine may flip over.
Another drawback to conventional directional controls is that a manual lever controls a manual valve to change directions. The manual lever and manual valve require substantial operator force to operate, also contributing to operator fatigue.
Some of these problems are exacerbated by the fact that other controls are similarly relatively inaccessible and/or hard to operate. For instance, dump controls typically take the form of hand-operated levers which are spaced a substantial distance from the handgrips and which therefore require the release of one of the handgrips for their operation. Some power buggies attempt to alleviate this problem by supplementing the hand levers with redundant foot levers. However, operating the foot levers requires the shifting of the operator""s weight to one foot with risk of loss of balance.
All of these factors conspire to render the power buggy relatively difficult. At the very least, the operator risks substantial discomfort in operating the machine.
Some power buggies have a hydraulic pump cooling fan to cool the pump because the pump is underrated for use with a power buggy and, accordingly, is routinely worked hard enough to require cooling via a cooling fan. Cooling fan failures are commonplace. Moreover, installation of the cooling fan on the power buggy requires additional assembly steps to align the gasoline motor and the hydraulic pump. In such a conventional buggy, the motor and pump, each of which had a shaft, were hard mounted to a mounting plate, which required almost perfect alignment of the two shafts.
The need therefore has arisen to provide a power buggy that can be operated easily, safely, and comfortably while at the same time maximizing vehicle stability.
A power buggy is provided that comprises a plurality of wheels and a movable chassis which is supported on the wheels and which has front and rear end portions. A dumpable article support is supported on the front end portion of the chassis. Also included in the power buggy is a pump assembly that has an axial piston hydrostatic pump which supplies power to the wheels and a second pump which charges a hydraulic system of the power buggy. The power buggy also includes an operator""s handle that includes first and second handgrips designed to be grasped by an operator""s hands.
A bucket dump control switch arrangement, a kill switch, and a directional control switch preferably are located at least in the vicinity of one of the handgrips so as to permit the operator to effect directional control, speed control, and bucket dumping control while holding onto both of the handgrips.
The handle preferably also includes a squeeze lever that has a lever portion and a pivot portion. The pivot portion includes (a) a free end that is pivotally mounted on a handgrip of the power buggy, and (b) first and second legs that extend at converging angles from the free end and the lever portion, respectively, and that are joined to one another at a corner of the pivot portion. The pivot portion also includes a cable mount that is spaced from the free end and from the lever portion. Actuation of the squeeze lever propels the power buggy at a speed that is dependent upon the magnitude of squeeze lever pivoting.